1. Field of the Invention
The present invention is related to storage file systems within computer systems, and more specifically to a system restore methodology that restores full and incremental backups using multiple simultaneous device streams.
2. Description of Related Art
In large-scale computer systems, after a catastrophic event such as a total system failure or when a software upgrade must be backed-out due to problematic changes to the operating system or other components of the software, a full file system restore may need to be performed. When a full system backup is available, the process of performing a full system restore is typically streamlined by writing large sequential chunks of restore data to the storage containing the file system to be restored. If the backup is be partitioned, e.g., into multiple independent volumes, the restore image can be written simultaneously from several backup streams, which are generally provided from slower devices such as magnetic tape storage devices. Since the backup devices are typically the limiting bandwidth for the restore process, using a larger number of backup devices reduces the time required to restore the file system.
However, in a typical system backup management scheme, a full backup is performed at predetermined intervals, e.g., weekly intervals, and incremental backups are performed more frequently, e.g., at the end of every business day or on an even shorter interval. If the backup being restored requires several incremental updates, then the restore process can be slowed significantly by having to apply the full system backup and then each incremental backup. Further, a full system backup with incremental backups are not typically restored from multiple device streams, since the incremental backups take precedence over the full backup and any earlier incremental backups.
Therefore, it would be desirable to provide for restoring full and incremental system backups together using multiple device streams.